Please visit the accompanying website: Life on Nu Phoenicis IV, the planet Furaha.
This blog is about speculative biology. Recurrent themes are biomechanics, the works of other world builders, and, of course, the planet Furaha.

Tuesday, 24 December 2013

Ahead of the normal schedule, and with dinosaurs, rusps and biomechanics!

Click to enlarge; copyright Gert van Dijk

The title of this post sounds like that of a proper scientific paper, doesn't it? Something out of the 'Journal of Astrobiological Biomechanics', I guess. It's time to look at rusps again. My big rusp painting is finished, and as it is meant as a double-page spread, it is large: 7200 by 2700 pixels. A spoiler is shown above showing a fragment of a rusp in the background of the painting. The fragment has been halved in size and its area represents just 2% of that of the entire painting. The painting is based on earlier sketches. For more on rusps, either visit the main Furaha site or look at these posts: sketches, anatomy, predation, concept paintings, etc.

The evolution of new Furahan animals gets more complicated with time. In
the beginning I just sketched a pleasing shape and started painting
right away. Now, I worry more whether the animal makes evolutionary, mechanical and ecological sense.
Well, up to a point; this is science fiction and supposed to be fun,
after all.

Here are some of the steps in rusp 'ontology': they started with some quick sketches, and then the slow evolution began: successive legs were offset medially and laterally to avoid legs bumping into one another, followed by an arrangement for their skeleton. Their fore and aft whips are long and held horizontally rather like the tails and necks of sauropods, and hence have a similar system of internal trusses as compressive elements at the bottom and ligaments at the top to withstand tensile stress. The whip is held up passively by these forces, so avoiding the high cost of doing that with muscle force only. The last stage involved refining the head of the rusp, and in particular its snout, or 'rostrum'. In an earlier post this rusp species was called Mammoth Rusp / Megacrambis, but now it is the Brontorusp / Brontocrambis; yes, that means 'Thunder Caterpillar'! The Mammoth Rusp still had some intricate limbs functioning as additional feeding aids under its snout. I was not too certain of that arrangement, and my doubts were confirmed by comments on that post. So the Brontorusp no longer has these additional mouth parts. The thing is, now we have a massive animal with a large head. How does it feed itself?

The mouth of the rusp is in its head, which seems obvious but in speculative biology not many things are obvious. Also note that rusps are large herbivores: they need a lot of food and spend much of their time eating. Moving about is costly, so it would be best if they moved the least possible amount to get their food, which does not sound as if there is much room to save energy. Let's tackle that by considering the problem of getting an animal's mouth on vegetation; there appear to be four solutions to do so; rusps use the fourth, but we'll come to that. The first solution, always necessary as vegetation will not come to you, involves walking to the food source.

But once an animal arrives at its 'foraging station' a nice way to save energy is to keep most of the body motionless and to have a long neck allowing the head and mouth to move about independently of the gut. For very large animals, needing to feed all day, it pays to divide their anatomy in mouth and guts; the rest is just 'other bits'. Sauropod dinosaurs used that method, and the image above is from a study on how far sauropod mouths could reach, depending on neck length and leg length. The idea is that the neck can move in a horizontal plane 90 degrees to the right and the left, and in a vertical plane straight up and down. If the animal is lying on the ground the volume of space that it can reach is one quarter of a sphere. If the base of the neck is higher up, when the animal is standing, the volume increases. The authors assume that the bottom part of the volume then is cylindrical whereas I would assume that to be spherical as well, but never mind.

Click to enlarge; copyright Gert van Dijk

Swans and geese have very flexible necks and can probably reach every point within that envelope, but if an animal has a neck less flexible than a swan's, only part of the volume is accessible to the mouth. If this is the first time you realised that geese and sauropods might have long necks for a similar reason, good!

The image above shows an adapted 'forage volume' for a sauropod: the outer red sphere is the outer limit of where it can reach, and the inner blue sphere represents the inner limit, assuming that the neck is too stiff for the animal to reach a point closer to its body. The human ('Marlene') is just there to keep the sauropod in its proper place.

The third solution to get the mouth near food is to use an appendage to shovel food towards the mouth. The best example I can think of is the elephant's trunk, which greatly increases the elephant's reach. The erstwhile rusp mouth limbs were short and not at all good as harvester limbs, and I did not wish to elongate them tenfold; they are gone. I also did not wish to turn the whip into a grasping organ. Rusp whips are not built for that, although in a pickle they can probably be used to knock a branch off a tree. Instead, rusps use a fourth system which is really just a combination of the last two: they carry their mouths towards the food without moving the rest of the head. The 'mouth extender' is extensible and based on a mechanical linkage system. In itself this is certainly not a new idea: Earth fish have such systems in abundance.

Click to enlarge; copyright Gert van Dijk

This image shows a schematic view of the rusp rostrum. Start with the red shape in the foreground: it consists of two V-shapes starting from a vertical axis. All places where elements meet are in fact joints. The pink axis shows that the whole ensemble can rotate, but it can do other things as well: if the two Vs rotate towards one another, the whole shape will become longer and narrower. At its right end, the shape ends in two points on a horizontal line. Now copy the shape, rotate it by 90 degrees, and you get the blue shape in the foreground. The two points where the red shape ends act as connection points for the blue shape. Once connected, some movements from the red shape are connected to the blue one, but not all, and that makes the rusp rostrum quite versatile. In the back you see how the rostrum is formed by stringing red and blue shapes together. In reality the trusses are not formed by straight bones, but by curved ones, so the section of the rostrum is circular rather than rhombic. The cylinder on the right attempts to show the outlines of the bones on a cylinder.

Click to enlarge; copyright Gert van Dijk

And this image shows an as yet unmentioned aspect of movement: if the two starting points are brought closer together, this changes the section of the rostrum as well as its length. The right one is extended, the middle one shortened, and the right one is in neutral position. I expect rusp rostra (yes, that's the plural) to be able to double in length.

Click to enlarge; copyright Gert van Dijk

But we need more flexibility, and that is achieved by rotating the shapes and using the angle between the Vs for additional control. The stylised skeleton in the back shows what can be achieved. So there we are: an extensible and steerable system to get rusp mouths where they would otherwise not reach.

Click to enlarge; copyright Gert van Dijk

Here are two views of an adapted Sculptris model of a rusp head. I take it you will recognise the system of trusses under its hide.

Click to enlarge; copyright Gert van Dijk

And finally, a schematic rusp foraging volume, rather like that of the sauropod (the whip of this model is truncated). Note that the rusp can access a larger portion of the outer foraging volume than the sauropod. The volume itself is smaller though, as rusps are smaller than sauropods, and their rostra extend their reach, bot nearly as much as the sauropod's neck does. Marlene is standing in the forage volume, something I would definitely NOT recommend! In practice, rusps are ground feeders, not bothering about high branches. Have I told you about the ecology of the spotted plains where they live, where post of forests alternate with plains and how rusp feeding habits are to blame for that? No? Oh well, that is another story.

Saturday, 14 December 2013

Sometimes I like to revisit sites to see whether there is anything new. In this post I will show a few interesting species that came up in this way. The site in question was visited in 2010, and shows the work of the Japanese author and illustrator Satoshi Kawasaki. He specialises in palaeontological illustrations but does not shy away from extending the time line of his work well into the future, up to 200 million years from now, in fact. In palaeontological papers and books you sometimes read 'mya' as an abbreviation for 'million years ago'. As the world of speculative biology is less hampered by ugly facts, perhaps it could profit from having a similar term for 'million years from now': myfn, or perhaps 'million years on': myo.

Click to enlarge; Copyright Satoshi Kawasaki

As I wrote before, Mr. Kawasaki has the sense of humour that allows him not to take his creatures equally seriously, something I like very much (I find mere monsters boring). Some of the animals on the pages showing life 100 and 200 myo are apparently drawn by other artists than himself, so het lets others play along, another nice trait. I would have like to exchange emails, but previous attempts to contact him failed. Let's have a look at some of the creatures.

Click to enlarge; Copyright Satoshi Kawasaki

In Google's translation this one is called 'Nereusu'. By omitting some of the Japanese characters I found out that Nereusu is simply a transliteration of the Japanese characters, so I could not translate it. I therefore suppose the name refers to Nereus, the mythical being from classical Greece Nereus, who was after all as sort of sea god. Somewhat ironically, there is of course another Nereus in speculative biology...

Anyway, the animal is obviously a large marine predatory bird descendant (probably descended from penguin stock). Students of speculative biology will note that such creatures are very abundant in fictional future seas, as they apparently tend to evolve in the minds of many creators. I do not really mind if such a concept is not completely original; after all, all of science fiction is full of common ideas. While I applaud originality, there is also pleasure in seeing a job well done. Mr. Kawasaki is a very adroit illustrator, and this is an excellent 'future orca-like penguin-descendant marine predatory beast'.

Click to enlarge; Copyright Satoshi Kawasaki

Have a look at this drawing, and you will probably guess what it is about without having to read the text. It can only be a social crab modelled on the pattern of ants, bees and similar colony dwellers. There is one giant 'mother' laying lots of eggs, here very neatly held in a redeveloped abdomen. The ones in the front must be soldiers, and the little ones in the middle must be workers. I cannot see whether or not they have pincers, but assume they do; otherwise, what will workers work with?

Click to enlarge; Copyright Satoshi Kawasaki

Sometimes Mr Kawasaki works on a theme; in my previous post I showed terrestrial cephalopods (I know, I know...), and this time I will focus on a group of his animals that do not seem to enjoy the common attention of future evolutionists: starfish! There is only one on the 100 myo page, shown above. It is not drawn by Kawasaki but by someone else. It may also be the most original of all the future Asteroidea ('starfish'). You cannot beat Google Translate for creating a sense of wonder, particularly where one was not intended: "One of the arm portion becomes large, the remaining portion forms a head lump pseudo part." I guess we would have guessed that anyway: four of the five original arms have shrunken and are now appendages around what is now a proper head. As a result, the animal is now bilaterally symmetrical. I do not quite see how evolution would set off in this particular direction, but like the result. I do not think I have seen anyone else designing this before, either.

Click to enlarge; Copyright Satoshi Kawasaki

The world of 200 myo has more future Asteroidea.The one above is a pseudoplant, a Parasasuteru. It lives in Australian swamps and -I think!- envelops animals moving in its shade, only to digest them at leisure.

Click to enlarge; Copyright Satoshi Kawasaki

And finally, one I rather like: the 'Di pedal stell' ; could that be a 'bipedal star', I wonder? If you count the number of limbs, you will find six rather then five, but the texts suggests that one of the original arms has split to form two legs: "Part of the two-that looks like a foot is what arm once was transformed." Probably. Have a look at Mr Kawaski's site for other interesting creatures, or, if you like palaeontological illustrations -who doesn't?- visit his pages of the past world.

And now something somewhat different
I have been looking for other projects of speculative biology, but have not found any new ones. I searched in various languages, albeit my skills are limited to Germanic and Romance ones. If readers know of projects that deserve attention, let me know, particularly ones I am likely to miss, such as ones in Slavic or non-European languages.

Finally, I have begun considering ending this blog. It is in its sixth year and I feel that some of the freshness has gone. The number of readers has not diminished, by the way: it is stable and in fact grows slowly. I find it a bit more difficult to come up with new subjects, and after more than five years the blog has perhaps become a fixture in the little world of speculative biology, not something that attracts much attention. Perhaps blogs are a bit like television series; at some point you stop caring about the characters, and that may be the time to consider a final episode.

Sunday, 1 December 2013

Readers who have followed my series of posts on alien plants and photosynthesis (here, here and here) will know that I have no objection against plants on other world not being green, so that is why there is 'red' in the title of this post. But this post will not be about photosynthesis, as I think that theme has been dealt with sufficiently. The next theme on plants will probably be about biomechanics, but I have not started that one yet.

This post is about portraying alien plants. Obviously it is possible to do a painting, and that is fine, but it is also a lot of work. Can't computers do part of the work? There are not that many software choices available to populate a landscape with alien plants. The one I have been using over the years is Vue by E-on software. Vue is difficult to handle, in part because there are many options that are not all well-explained in the manual, but also because the software can be very unforgiving depending the hardware you are using. In other words, it may crash. It is the kind of programme that you can easily develop a love/hate relationship with.

It has an ecosystem feature, in which you choose plants or objects, adjust their rations and relative sizes, and when you then press 'populate' the programme does just that. It can even take matters such as height or slope of a landscape into account, placing some species there and others not. The problem in designing alien forests was that Vue's innate plant designer was inadequate: it let you design variations of Earth plants, but made it impossible to design something more interesting from scratch. For that I used XFrog 3.5, a programme that allows the user to come up with intricate new shapes. The XFrog plants could be imported into Vue, and did allow worlds to be populated with alien plants. Some examples of my earlier efforts are here for Epona and here and here for Furahan swamps.

However, there was one disadvantage: Vue's own plants could sway in an imaginary wind, but the imported XFrog plants were static objects. For static images that is obviously not a problem, but for animations a forest in which no leaf moves is just odd. I have stopped doing Vue animations for that reason.

Recently, E-on introduced a new programme: The Plant Factory (TPF), which does let the user design plants from scratch, with the promise of having the result sway the wind. That was attractive, so I decided to try it, even though the user forum made it clear that this is a typical E-on product: it can do amazing things but often in a roundabout or unexpected manner, and sometimes it simply does not deliver. TPF has no manual whatsoever, so anyone wishing to use it should treat it as a voyage of exploration rather than as a productivity tool. There is a 'personal learning' version, so everyone can test it without spending (rather a lot of) money on it.

Click to enlarge; copyright Gert van Dijk

I first tried whether I could make it design oddly shaped plants, and here is one of first attempts. I tried to obtain a results resembling an earlier XFrog design, and that went reasonably well, as you can see above. As you can see, this tree has its major branches growing from a central trunk as do Earth trees. Its branches curve through the air to reach the ground, where they may take root, providing water and nourishment or simply offer structural support. The proportions are not right yet, it is a start.

Click to enlarge; copyright Gert van Dijk

The image above shows a hillside populated with two species of simple plants, home made in TPF. The scene was intended to experiment with wind animation. The first result was disappointing in that there was hardly any movement. There are lots of sliders controlling wind, which I had left at their original settings. Apparently those are meant for an unnaturally calm day. Very well, let's turn the wind setting up to 100%. That did not do too much either. I remembered an earlier surprise in Vue, dealing with lens blurring; there too a setting of 100% was almost negligible; someone at a forum told me to not to treat 100% as a limit, and so here too I set wind animation to 500%, and now at least the leaves move. Apparently this is more or less a dimensionless unit; just one of those odd Vue quirks.

And here is the result; better, I think! It's not a storm yet, but at least there is movement! The quality of videos on blogger is not very good, so it can look a lot better. Meanwhile, there is still a very large number of options to discover or, given the lack of a manual, to blunder into, so do not expect a to see a marblebill brachiating through a Furahan forest. Not quite yet, anyway.

Sunday, 17 November 2013

I have not discussed the theme of walking machines for a long time: the last post on that subject was published back in 2010, but dealt with 'radial robots', meant as toys. As you will know the word robot was derived from 'worker', so it is fitting to go back to posts on robots meant to do proper work (here).

The lack of interest was not because no progress is being made; quite the contrary. There is so much improvement that robots are slowly taking on aspects of animals, and the reason for that is en ever-increasing subtlety of control of the movement. The word 'cybernetics' has its origin in a Greek word for 'steersman', and 'steering' all aspects of movement is a key concept in walking, regardless of whether you are talking about an animal or a machine. The other major theme is mechanics, of course. For some background on leg design, see here and here.

You are probably familiar with 'Big Dog', a walking robot made by Boston Dynamics. That company has developed a range of robots meant to aid the military. The video above shows the level of control their robots have these days: clearly, this thing, the 'legged squad support system' (LS3) can hold its won on difficult terrain and follows its human master on its own. There are more YouTube videos (and with better quality) that are found on YouTube after a search for 'Boston Dynamics'.

Here is another one: a 'cheetah' running very fast on a treadmill. It is tethered and the power source is external, but is still an amazing sight. It is interesting to see how the engineers handled the problem of elongating stride length. Running mammals generally have legs with three major segments; the foot can be seen as a fourth, minor segment. Cheetahs obtain an additional lengthening of their strides by flexing and extending their bodies as well during the stride. Now compare that to the cheetah robot: it does have a flexing body, but the legs have only two segments and the foot appears to be something like a rubber ball only.

Their latest attempt is called 'WildCat', which is apparently based on the cheetah design. This time both the front legs and the hind legs seem to be linked to the main body by a flexible joint, instead of the legs being fixed to the body directly as was the case for LS3. As a result, the setup is beginning to resemble the setup of shoulder and pelvic girdles common to vertebrates.

The legs still consist of two segments only. Seen from a level of control, having only two segments makes it much easier to find out where the foot should be, as only two angles have to be controlled, and each foot position can be reached with only one combination of angles. If you add another segment, each foot position can be reached in an infinite combination of joint angles. I wonder whether the lack of a foot is due to similar considerations: adding another segment, even a short one, probably adds a considerable computing overhead.

Another interesting aspects is how the engineers chose the directions where the knees and elbows point to. In an earlier post I discussed whether legs should start with a segment pointing forwards (a 'zig') or backwards (a 'zag'). The next segment than points the other way. The upper arm (humerus) of mammal front legs points backwards and the forearm forwards, so the mammal front leg is a 'zagzig'. Hind legs, in the same jargon, are 'zigzags'. The formula for the entire mammal is a 'zagzig / zigzag'. Are you still there? (Mind you, this is just a simplification paving the way to look at robots; if you include the scapula, -a zig!- and label all three segments, mammals are 'zigzagzig /zigzagzig' animals.)

Now have a look at the LS3 again. Its mid leg joints point away from the body, just the opposite of the mammalian leg bone pattern. The LS3 is a 'zigzag / zagzig' walker. WildCat, in contrast, is a 'zagzig / zagzig' walker. I have no idea why the engineers chose the designs they did, but the results strengthens my feeling that there is no basic overwhelming advantage inherent in the current mammal pattern. During evolution sideways-pointing legs were turned to have the plane of the leg parallel to that of the body, and in this turn front legs turned backwards and hind legs forwards. Evolution might well have resulted in a different pattern, that of LS3. At least it prevents knocking elbows into knees! Those who wish to add more 'alienosity' to their animals might consider departing from the Earth vertebrate pattern. Have a look at LS3, WildCat, or, of course, at an older post in this blog to see what might be done.

Finally, a word on gaits. Walking consists of a repeated cycle of leg movements, and a gait is nothing more than the phase differences between the various legs. The basic gait of LS3 is a trot, in which front left and right hind legs move together as one pair, and the other two legs from the other pair, moving exactly half a cycle out of phase. If this is confusing go the Furaha 'walking with...' page, where the major gaits are explained. The engineers of Boston Dynamics have managed to proceed beyond the trot, so the thing can bound and gallop as well. I am very surprised though that it seems to use a trot when it is walking very slowly. You would expect a 'walk', which in this context also is a defined gait. The various gaits used by animals have important energy consequences, and a trot is more expensive than a gait. I wonder how much further 'evolution' will take these robots. More segments? More efficient gaits? More legs, even?

Sunday, 3 November 2013

The last post on alien plants went into some fairly technical details about photosynthesis, and took a look at where the process could be adapted to make it more alien. Today's post has a closer look at just one aspect: leaves.

Photosynthesis obviously depends on catching light and is therefore a process that takes place on the surface of a plant. How much of a surface is needed will depend on many things, such as how much energy is needed. As related before, C3 photosynthesis can only make use of up to 25% of the light falling on them (well, at noon in the tropics, that is). Photosynthesis becomes saturated, doing nothing with that extra light.

For now, let's assume the presence of leaves on a planet of choice as very similar to Earth's broad leaves; flat structures of, say, 10 cm across. They need light, and so face the sun. But not every leaf of every plant will receive full sunlight: the sun moves across the sky (well, as far as the plant is concerned it does), other plants may be in the way, and even its own leaves, placed higher up, will take light away from lower leaves. A typical Earth leaf transmits only 5% of the light striking it. The next leaf down in turn absorbs 95% of the -little- light striking it, leaving only 0.05 times 0.05 of the sun light, or 0.25% of the light striking it.* On Earth the critical level for photosynthesis to be of any use is at about 1% of full sunlight.

It is therefore reasonable to assume that plants would have only one or perhaps two layers of leaves, right? Additional leaves would not contribute anything, and yet trees typically have many more layers of trees. The answer to this riddle is found in the efficacy of photosynthesis and a fact that you might not have considered interesting in this respect: the size of the sun.

Click to enlarge; source: http://en.wikipedia.org/wiki/Umbra

The image above shows the umbra and penumbra as commonly illustrated in astronomy books. The sun is not a point source of light but a sphere much larger than the Earth. Rays of light depart in all directions from any point on its surface, to the effect that there is a conical volume of space behind the Earth where the rays cannot reach, or, in other words, from where an observer can see no part of the apparent disk of the sun. That conical volume of space is the 'umbra' , simply meaning shadow in Latin. Around it there is an area from which an observer can see part of the sun's disk, so that area receives some direct sunlight, but not full sunlight: the 'penumbra' (nearly shadow). Everywhere else receives full sunlight. The length of the umbra cone depends on the diameters of the Sun and the Earth and the distance between them, as a few minutes experimenting with some sketches will show you.

The same applies for objects closer by. All you have to do is to look at the shadow of your hand as you raise it from the ground on a sunny day. Leaves also cast an umbra, an area without direct sunlight, where it would be best not to place another leaf. The length of the umbra can be calculated as explained above, and for Earth the calculations that the umbra is about 108 times the width of a leaf. For a 10 cm leaf that would boil down to 1080 cm, or 10 meters. As we will see the distance is shorter in practice. Leaves may receive enough light in the penumbra to work well. Remember that on Earth photosynthesis is already saturated at 25% of full sunlight, so photosynthesis can work at full capacity even with a fair amount of shade.

I wrote a Matlab program to have a look at how the umbra and penumbra could look for some artificial leaves. The distance between the Earth and the sun is 149,597,870,700 meters and the diameter of the sun is 1,392,684,000 m., both according to Wikipedia. A leaf takes up half the area of a 10 by 1-0 cm square area. In the program, this meant that I could paint half the pixels in a square area black denoting the leaf. All the program does is to cast ray from a raster of points on the sun's disk to all points on the leaf area, and to see which rays are intercepted and which are not. I did that for three distances behind the leaf: 0.5, 1 and 5 meters.

Click to enlarge; copyright Gert van Dijk

And here is the result of a simple roughly circular leaf. Half a meter away our leaf casts a recognizable shadow. I calculated how large the area is that receives less than 25% of full sunlight. That value of 25% is randomly chosen but helps to indicate deep shadow. Depending on the efficacy of photosynthesis, the value could indicate the lower limit of light for photosynthesis to work if it is particularly inefficient, or perhaps the point at which its efficacy becomes impaired. At half a meter an area of 85% of the original leaf receives less than 25% of full light, while at one meter the area decreases to 69%; at 5 meters it is 0%.

Click to enlarge; copyright Gert van Dijk

Let's try with a differently shaped leaf. After all, the umbra depends on the width of the leaf, so a leaf with a thinner shape should do better. This cross-shaped leaf was somewhat disappointing, as its values for 25% full light were only slightly better than for the circular leaf. For 0.5 meter the value was 81% of leaf area, for 1 meter it was 65% and at 5 meters it is 0%. Clearly, some more shape experimentation is needed.

Click to enlarge; copyright Gert van Dijk

This 'clover' has more space between its petals. Does it work better? Yes it does: 0.5 m results in 62%, 1 m in 31%, and 5 meters as usual results in 0%.

Click to enlarge; copyright Gert van Dijk

Finally, here is the ultimate feathery leaf, designed to have thin strands, while its area is still the same as that of the others. Here are the values: for 0,5 meter, only 11% of the leaf area receives less than 25% of full light, and at 1 and 5 meters the value is 0%.

So, what does all this mean for the design of trees on other worlds? Firstly, like on Earth, you can have multiple layers of leaves and still have enough light trickling down for lower leaves to be useful. The shape of leaves is also important. Apparently some Earth trees use this effect: the outer or upper leaves of olive trees are thinner than the leaves lower down, which makes sense in view of the experiments above.

An interesting consequence is that the distance between leaf layers would depend on the apparent diameter of the sun's diameter as seen from a planetary surface. Doubling the diameter would half the length of the umbra, so leaves could be closer together and still receive an adequate amount of light.

Should your alien trees have a few layers of leaves or multiple ones? Theoretical considerations on Earth suggest that fewer layers work better when the amount of light is low to start with: the absolute level decays very quickly with the number of layers. For alien worlds, 'low light' can probably be rephrased as a low capacity to make use of available light. That could be low light with good photosynthesis or good light with poor photosynthesis. The effect of changing the saturation point is more difficult to predict. On Earth, where photosynthesis saturates at only 20-25% of full light, shadows may still leave enough light. But if photosynthesis could use up to 75% of all light, the top layers might generate all the energy needed, so more layers would be superfluous. Then again, the plant might well have evolved to use all that energy, so perhaps lower layers would still be useful.

No doubt, additional demands, such as transport of metabolites and structural stiffness will complicate the picture. Nevertheless, on Furaha various plants carry their leaves in umbrella-like shapes, in which two or three layers of leaves form a nearly completely closed canopy, closing off the sky to potential competitors that might grow up beneath them.

The good news is that it is now available for free as a pdf file. The resolution is fairly low, but it is free. There may be a digital version for Kindle and other devices in the future. I will keep you informed when there is news of that. Here is a direct link to the pdf file.

Sunday, 13 October 2013

There still is no time to write anything extensive. I have plans for chapters on 'exobotany', having read enough about plants on earth to begin thinking about which aspects where evolution might take things in another direction. But those kind of posts require quite a bit of time, so they will have to wait a bit longer. Instead, another quick visit to the Archives of the Institute of Furahan Biology, those cavernous halls filled with sketches of animals that mostly never saw the light of a fictional sky...

As the analogy is beginning to show signs of severe stress, let's have a look at some sketches instead.

Click to enlarge; copyright Gert van Dijk

The Scuttle A scuttle, or at least that is what I wrote alongside it. It is definitely un unclassifiable life form, without apparent link to extant Furahan Clades. It's certainly not a Fish, and it does not seen to be a hexamere at all. There are four fins, it would seem, although the aft ones differ so much from the front ones that it is doubtful they share the same basic anatomy. Then there are two vertical fins that also de not seem to share structural similarities with the other fins. The head certainly is odd, with six eyes in two rows, and a mouth flanged by two, well, flanges. Their purpose is not immediately obvious, and there do not seem to be recognisable jaws. The animal as a whole seems to be a fairly fast swimmer, but otherwise it is had to tell what it eats or what is does.

Click to enlarge; copyright Gert van Dijk

Caecus panopticusThis one, in contrast, is easily recognisable as a tetrapterate, a four-winged avian of hexamere stock. Having four wings poses interesting problems for an avian on the found or sitting on a branch, as this one is doing. In later avian developments I worked out a different folding pattern, one that differs more from the Earth bird pattern shown here. The later design still allowed the front wings to be folded on the outside of the larger hind wings, though. This particular animal cannot be taken too seriously, with its oversized head and beak. Still, take a look at a marabou or a toucan, and you will find that earth birds have also produced forms that, if not true, would be ridiculous.

That holds for this 'Caecus panopticus' as well. The genus' name was derived from a superficial resemblance of the eyes with dark glasses, seen from the side. The animal is not blind however, as its name suggests, but had quite good eyesight, in common with all Furahan avians.

Click to enlarge; copyright Gert van Dijk

Here it is again, now with a tentative colouring underlying the sketch. The colours do not make it look any more serious, but it is not meant to be that anyway. Speculative Biology can do with a bit of humour, I think.

Sunday, 22 September 2013

The Archives contain many sketches of animals with a Bauplan that seems to be at odds or even at ends with the 'canon' shapes of Furahan life forms. Some are actually upgraded to 'canon status', such as rusps. I picked two of them out for today's post, a short one, as work is encroaching ever more successfully upon free time.

Click to enlarge; copyright Gert van Dijk

The TakkebeestAnyway, this one was labelled 'takkebeest', and as 'tak' means branch and 'beest' means beast, it is a branchsitter (there's another meaning too, as 'takke' can also stand for 'irritating' or 'bad'). I rather like its general shape, destined to more or less confuse the viewer. You can see that it has toes that branch following the 'Devonian pattern', stemming from a rather fat body. The upper body is equipped with asymmetrical claws. Above that, well, its mouth is separated from its eyes by a long neck. And why not? Cats can hardly see what's right in front of them, and do quite well, so why can't a takkebeest rely on propriocepsis (that's feeling where your limbs are) to deliver morsels of food to the mouth? Come to think of it, humans can't see their mouths either. Later a development of the takkebeest was fully developed for a painting, so this particular Bauplan was elevated to official status. That makes it 'classifiable', but I have not yet thought of a name for the group ('Takketheria'?).

Click to enlarge; copyright Gert van Dijk

The Meralgian NutcrackerThis one I labelled in English; as I realised that a book on Furaha would never be published in the -too small- Dutch market, at times I made notes in English. I think it only has four legs, so it is not a hexapod. Indeed, there is mention of it being related to the honeysucker, and that is four-legged as well. Its mouth carries impressive looking teeth, that must be designed to crush nuts. Having heavy equipment at the end of a long snout must have consequences as far as moving the head is concerned but the nutcracker looks rather solidly built, and must be able to carry this off. Nothing has been done with the design since, but it's cousin is there, showing that there are more body schemes on Furaha than you might have realised. Is that unrealistic? I doubt it: if you start counting the various invertebrate body schemes on Earth, you will find that there are many. on Earth, there are just not many large animals with different body plans; there are on Furaha...

Above you see the specimen of 'Fishes II' that was shown in the previous post. It was digitally sculpted and painted in Sculptris. Such sculpts help define the perspective of the undulating fins. Once you have such a shape in your computer, you can go two ways: the first is to perfect digital sculpting, which at present probably means mastering ZBrush. That road does result in a 2D image, taken as a snapshot of the model, but do do that the models need to be sculpted with much more finesse that the rough ones I produce. Readers of this blog will know the work of Marc Boulay, who does all this at the expert level.

But I chose to stick with regular figurative painting, because there is something about a painterly look that I like. It is not that easy to define 'figurative painting' in such a way that it excludedes digital sculpting. Perhaps it is creating the illusion of a three-dimensional object by placing colours on a two-dimensional surface. This includes digital painting as well as classical painting using oils or water colours or any such technique (I sometimes encounter a resistance against digital paintings in art circles, which must mean they see it something else than it is: just another technique).

In this process, 3D sculpt programs are aids to get the perspective or the lighting right. As with any technique they have their own unique problems. People will accept any perspective on a photograph or computer rendering, but not on a drawing (see here for an explanation).

Click to enlarge; copyright Gert van Dijk

Anyway, I try to produce a painterly effect. The two images above show two versions of the head of the Fishes II species Vexilloscissus. The left one was based on the 3D sculpt. I thought the painting was finished, and suddenly realised that there was no way that the six protojaws seen here could evolve into the typical four jaws of the basic terrestrial hexapod Bauplan. That design involves upper and lower jaws with two rows of teeth each, and two lateral jaws with one row each. While sculpting I had forgotten that, so I had rotated the ensemble of six jaws incorrectly, with jaws in the midline in the upper and lower positions, and no jaw in the lateral positions. In world building it is hard to keep tracks of all the details, or at least that is my excuse for the mistake.

So I had to erase the jaws and paint them again in the correct position. The result is at the right. It's a pity really, as I rather preferred the left one. Oh well, never mind...

Saturday, 17 August 2013

More ballonts? Well, yes: I had previously explored whether it is possible to produce a fairly small life form floating around using the lighter-than-air mechanism, but there were some loose ends left. As the last one was posted in 2011, it may be wise to recapitulate a bit (or work your way up from here, through here, to this one).

Click to enlarge; copyright Gert van Dijk

The image above show a scene on Earth on sea level at about 20 degrees Centigrade. A default local sophont (let's call him 'Julius') holds a stick indicating two meters. There is also a balloon with a radius of 62.03 cm. Why 62 cm? Because that yields a sphere with a volume of exactly one cubic meter (m^3). The skin is made of a 0.1 mm thick mylar-like material with a mass of 0.5802 kg. The balloon is filled with the lightest possible gas, hydrogen. Hydrogen has a density of about 0.0899 kg/m^3 at 20 degrees, while the air has a density of 1.2019 kg/m^3. So, the 1 m^3 balloon has 0.0899 kg of hydrogen in it, while the corresponding volume of air has a mass of 1.2019 kg. The balloon can therefore lift 1.2019-0.0899 = 1.1120 kg (that is the part needed to understand how balloons work). As the skin masses 0.5802 kg, that leaves 1.1120-0.5802 = 0.5318 kg to build a nice body out of. That is not a nice big body at all; given a body density of 1.1 kg/m^3, which is like our bodies a bit heavier than water, we can hang a spherical body with a radius of just 4.9 cm under our balloon, and the ensemble will then just float. Of course, a real animal would have tentacles and limbs and mouthpieces etc.

As said, I wanted ballonts with a body mass of, say, 10 kg but with only a moderately sized sac. As the example above shows that does not work on Earth. The hydrogen inside the balloon cannot be made lighter, but we can alter the atmosphere outside it; this is speculative biology after all. There are two ways of doing so: the first is to stuff the atmosphere with very heavy gases such as argon, but such elements are quite rare in the universe. The other is to add mass by increasing pressure, as that will squeeze more mass in the same volume. So, let's explore gas giants, where high pressures are easily found.

The pictures above show information about 'our' gas giants: the composition of the atmosphere, the temperature and the pressure. Not surprisingly, atmospheric pressure increases the deeper you descend into the atmosphere. For our first try, we should perhaps be a bit conservative and stay with biology in fluid water. A temperature of 20 degree centigrade should not upset Julius; it is the same as 293 degrees Kelvin. For Jupiter, the 293 Kelvin zone results in an atmospheric pressure of some 9-10 times that of Earth, which sounds like a decent start. Instead of jumping in directly, it may be easier to take it in stages, building on the Earth model shown above.

Click to enlarge; copyright Gert van Dijk

The image above shows the first step: Earth's atmosphere is changed to a Jovian one at one atmosphere and 20 degrees centigrade. Internet sources show that the Jovian atmosphere consists of about 86% hydrogen, 14% helium and a smattering of other compounds. Based on the densities of hydrogen (0.0899 kg/m^3) and helium (0.1664 kg/m^3) the density of a 86:14 hydrogen/helium mixture should be 0.1006 kg/m^3. Oops! That is only very slightly denser than pure hydrogen, which we need to fill the ballont with! If you thought Earth air was a bad medium for ballonts, think again. So what are the effects? Well, the liftable mass is 0.1006-0.0899= 0.0107 kg. Remember that the skin had a mass of 0.5802 kg? There's nothing left for a body, so this balloon is not getting off the ground at all.

Click to enlarge; copyright Gert van Dijk

We were aiming for high pressures, so let's increase the pressure to 10 atmospheres. The mass in the balloon will be 10 times higher, and so will the mass of the equivalent volume of air. So the liftable mass also becomes 10 times larger: 10 x 0.0107= 0.107 g. That's still nowhere near the mass of the skin, so this balloon isn't going up either.

Click to enlarge; copyright Gert van Dijk

Let's leave Jupiter and find a ballont-friendlier place. Uranus and Neptune have atmospheric pressures about 50 times Earth's at the 293 Kelvin range. That's better, and apparently the Uranian atmosphere is heavier, with 2.3% methane thrown in. I make the density of its mixture to be 0.1148 kg/m^3 at 1 atmosphere and at 20 degrees C. So, the 1 m^3 balloon can lift 0.1148-0.0899 =0.0249 kg. That is not good enough, but at 50 atmospheres the liftable mass is 50 times that, or 1.2450 kg. Subtracting the skin leaves 0.6648 kg. Finally, a floating balloon! Hurrah!

Or perhaps not 'hurrah', as that is only a tiny bit more than what we had on Earth to start with... Let's go up to 200 atmospheres in Uranus: the liftable mass, skin already subtracted, would be 4.4 kg, and at 500 atmospheres it would be 11.9 kg. Finally we have what we wanted!

Well, not really; these values are not yet adapted for the lower temperature. Julius is left behind, as we need a wholly new biochemistry. The atmosphere is now also so soupy that you would not want to think about the wind or moving in it. Adding even more problems, there is another potential disaster lurking in these gas giants: gravity. The gravity constant for Uranus is nice at 8.85 m.s^-2, a bit less than Earth's at 9.8 m.s^-2. But Jupiter has a value of over 25, so if you thought you could get away with a nice fragile ballont there, waving its slight tendrils through the air and looping in prey with slender tentacles, think again: the animal would need the sturdy limbs befitting a 2.5G environment.

It really does seem as if the universe is trying to sabotage ballonts, doesn't it? Gas giants do have high atmospheric pressures, but their beneficial effects are counteracted by the fact that the atmospheres consist of very light elements. It seems that the only way to get a viable (pun intended) ballont on a Jovian planet is to make the ballont extremely large. But that is where we started... I am beginning to think that there may not be any appreciable advantage in locating ballonts in gas giants, even though science fiction is full of them. They do about as poorly there as they do on terrestrial planets, meaning they can in fact work, but they have to be big, very big. Perhaps gas giants have other advantages for ballonts: there's certainly a lot of atmosphere to play with in them.

Ca I still claim that ballonts are so common in gas giants that they are boring? Yes, but they will be big, as usual; perhaps that's what makes them boring. The best way out for small ballonts seems to be offered by terrrestrial planets with heavy gases and high pressures: Venusian analogues? Perhaps there will be a 'Ballonts VI', one day.

Saturday, 3 August 2013

What you see here is a sketch of the 'aggie', the favourite prey of the marblebill. The pages detailing the marblebill in The Book have this to say regarding the aggie:

"The marblebill’s favourite prey is the ‘Aggie’ (Agitator augur), a tree-dwelling fructivore. Once caught, the victim’s feeble attempts at defence have little chance of success against the marblebill’s armoured chest and abdomen. There is little time for resistance anyway, as marblebills usually disarm their victims quickly by snapping its cervical medullae." "A troop of Aggies, admittedly not the brightest of beasts, may suddenly see a branch swaying and a baignac falling. Only when they hear the marblebill’s triumphant howl does it dawn upon them that one of their comrades had just now been sitting on that branch and been munching that baignac."

That's all that is known in the entire universe regarding the aggie. I have started sketching them several times, but was never too happy with the result. The sketch you see here is not the definitive aggie either. This particular one is a brachiator, just like the marblebill. The degree of adaptation of the marblebill to its arboreal brachiating life style suggests that its environment has been around for quite a while. If so, other species could be equally well adapted to an arboreal way of life. That does not necessarily imply brachiation (see here and here); the animal could be a jumper, a climber, or even a glider. But this one is a hexapod brachiator.

Click to enlarge; copyright Gert van Dijk

In previous versions I toyed with the idea of using the second pair of legs as the main. In fact, here is an old very quick and dirty sketch showing that approach (Brynn Metheny also did one once, the 'pygmy esorifleu', which I discussed previously). In the 'Mark I' the body is suspended from the middle limbs, and the front and aft ends hang down. It must have evolved from basic hexapod stock, and it is hard to imagine an ancestral species with six more or less equally-sized legs preferring to grasp branches with its second rather than its first pair of limbs. You can see the 'Mark II' next to it. That sketch was ancestral to the marblebill's design, and they still swing from their front limbs.

Click to enlarge; copyright Gert van Dijk

Still, there may be a way to evolve a brachiator with 'middle limb suspension'; take a typical Furahan neocarnivore, one of those animals exhibiting centaurism. As you may remember their first pair of legs are not used for locomotion but to catch prey. If such an animal started climbing trees, it might keep its weapons intact, and adapt its second and third pair of legs for locomotion among the branches. Its offspring could become either become jumpers of climbers, using four more or less equal limbs, but they could also turn into brachiators. If so, they would swing from their middle limbs and use their front legs as weapons. In my mind, I see the hexapod evolutionary tree sprouting a new branch even while I am writing this...Then again, a neocarnivore taking to the trees might use its spears or clubs to hook a branch. Being at the front of the body they are well placed to do so. If these limbs then become brachiating arms they would resume a locomotor function again; I see another evolutionary branch exploding into view with an almost audible 'whoomph'. By the way, that latter branch is also the first official example of 'decentaurism', or the reversal of nonlocomotor limb use to a secondary locomotor purpose.

Anyway, back to the aggie. Have a look at some of its features.

It sits upright, which may make sense for a brachiator: its body is held vertical while brachiating, and it might easily keep doing so at rest.

Its limbs are attached to the body with joints that allow three axes of rotation. The brachiating arms are attached to the body through a short bone that ends at the 'shoulder'. Unlike Earth primates, the shoulder girdle is attached through bones to the axial body skeleton rather than through muscles only, but the animal still needs thick muscles to control the position of the body with regard to the arm. The unfortunate result is that the attachment looks much like a primate shoulder girdle; parallel evolution or a limit of my imagination?

You might just make out the ancestral hexapod toe branching pattern (more about that here).

This particular aggie version has a pot belly. While sketching it I had forgotten about it being a fructivore with a preference for baignacs (remind me to show you a baignac one of these days). Fruits usually offer high quality food, so animals does not need many of them. While sketching I had low-grade food in mind, say fibrous leaves, and such food requires a lot of processing and a sizable gut. Specialising on low-grade food has the advantage that there will not be much competition, but the end point might be a slow animal that is not at all energetic: something like an Earth sloth. While sloths are preyed upon by harpy eagles, the dense parts of the forests are probably closed to eagles. But introduce the marblebill, and anything as slow as a sloth has a problem. So, the aggie cannot be too slow. It should probably lose its potbelly and resume a high-energy fruit diet. Of course, it should perhaps be better able to defend itself, or use its social skills, or perhaps...

...never mind; thinking about the aggie has once more led to interesting predators rather than their prey. One of these days I will design the definitive aggie; this is not yet it.

Sunday, 14 July 2013

'Alien Plants IV'? Where are the other 'alien plant' posts? Well, 'Alien plants I' and 'II' were published a long time ago, and 'Alien Plants III' was not labelled as such: that would be the post 'The black, black grass of home...' posted one year ago. That one was more serious than the first two, and dealt with the colour of plants on Earth. To be succinct: green does not equal photosynthesis.

As can be seen from the absorption spectrum of chlorophyll above, photosynthesis does not use the green portion of the spectrum, so that portion gets reflected for us to see. In doing so plants ignore much energy potentially available to them, as green is right in the part of the spectrum where the sun emits a lot of light. You might think that photosynthesis would evolve to make the most of the light falling on it, and, if so, you would predict that Earth plants should be purple (see the 'black grass' post for speculations why some bacteria are purple but plants are not).

Some people wonder whether we can predict the colour of plants on a planet by looking at the spectrum of its sun. Earth's example definitely suggests that we cannot, so I personally see no problems with filling hypothetical planets with plants of just about any colour; well, as long as the absorbed colour is present in that sun's spectrum, of course. A perfect photosynthesis process would be able to use light of every frequency equally well, with the effect that such plants would be grey or black.

After writing the 'black grass' post I returned to the question why it is difficult to come up with alien-looking plants. Intuition suggested that there would be only so much you could do with plant shapes: flat leaves fixed to the ends of a branching structure seem so sensible that they are probably universal, so plants everywhere would look similar. Perhaps so, but intuition is not a reliable predictor in science, so some old-fashioned studying was called for. I recommend 'The Life of a Leaf' by Steven Vogel, who also wrote a fine book on biomechanics.

The fun part will be designing new plant shapes, if possible, but before we get to that there is some work to do, I am afraid. This post starts with photosynthesis on Earth, to find out if it can be tweaked to produce plants with a high degree of 'alienosity'.

1. Efficiency of photosynthesis
The job of photosynthesis is to take water, CO2 and light, and turn out carbohydrates to use as energy sources and building materials, with O2 as a leftover waste product. Although the total energy capture by photosynthesis outranks human power consumption by far, photosynthesis is less efficient than the photovoltaic process used in solar panels. Photosynthesis is surprisingly inefficient. The image above is based on analyses done by scientists looking for ways to improve crop yield. The 'black grass' post explained that only a portion of sunlight is used for photosynthesis, and the papers show that portion to be about half of the available energy. The graph above states the efficiency of each step, which is which fraction of energy gets passed on to the next step. The efficiency of the first step is 0.5: of 100% light to start with, 50% is left. That's a big loss.
The efficiency of the next step is 0.9. In terms of the original amount of light 45% goes on to the next step. And so it goes on, multiplying all the efficiency factors in turn, step by step, until only about 5% of the original energy is left at the end. As I said, not impressive at all. I should add that this holds for the so-called C3 photosynthesis type. The C4 type does better, managing to end up at 6 to 6.5%. That does not seem like a big improvement, but it is still up to 30% better than C3 photosynthesis.

One biochemical step deserves additional mention: 'photorespiration'. The reactions that take in H2O, CO2 and light to turn them into sugars and O2 are not exactly simple; an important enzyme capturing CO2 is ribulose-1,5-bisphosphate carboxylase oxygenase (no wonder that it is called 'Rubisco'). Rubisco deserves to be known, if only because it is probably the most common protein on Earth. Its job is to speed up the reaction binding CO2 that ultimately ends in O2. Oddly, Rubisco binds quite readily with O2, driving a process in the wrong direction! This backwards process is called 'photorespiration' and has puzzled biologists a lot. Its presence suggested that it might have some use, but apparently plants do quite well in artificial atmospheres without any O2 at all, so photorespiration seems to be a gigantic and puzzling waste.

2. Bright light: photosynthesis saturation
As if the above series of limitations is not enough, there is another one: photosynthesis saturates. Photosynthesis normally increases with the level of light but only up to a point. If light intensity increases beyond that point, photosynthesis cannot increase with it (it may apparently even decrease to protect the plant). Whether this is an important limitation depends on where you are: to catching the maximum amount of light to reach the Earth's surface, you will have to stand at the equator, at noon, on a clear day. The C3 type of photosynthesis can only use about a quarter of the light there! If you were to add that step to the image above, the scheme would start with a giant loss of 75% right at the start. Seen in that light (pun intended) the overall efficiency of 5% becomes an even less impressive 1.25%.

Then again, it is a bit unfair to set light at noon in the tropics on a cloudless day as the standard. Living at higher latitudes, clouds and shadows from mountains or leaves will limit the amount of light that reaches a plant, so in many cases the saturation point will never be reached. That is fine for those plants, but the tropics are still there, and photosynthesis could do a lot more for tropical plants if their saturation point would lie at a higher intensity.

3. Shadows: the photosynthesis compensation point
Plant cells burn molecules with the help of oxygen to free stored energy and use that for their metabolic needs, exactly like animal cells. This process is called cellular respiration and does the opposite of photosynthesis. As the amount of light decreases, photosynthesis will be less effective and produce less oxygen, while cellular respiration keeps using it a stable rate. At some shadowy light intensity the two processes are matched: the compensation point. When light levels drop beyond that point, plants become net users of oxygen and energy instead of producers. Plants can survive that state and in fact do so every night, but over time there must be a net profit. There are many places, such as the floor of dense forests, where it permanently too dark for photosynthesis to work.

"It's photosynthesis, Jim, but not photosynthesis as we know it".
With all this in mind there seems to be ample opportunity to tinker with the process and design an alien photosynthesis. Mind you, photosynthesis could well be even less efficient on an alien planet than on Earth, and that possibility should not be dismissed out of hand. World builders have a strong tendency to design super-organisms, better than what Earth has to offer, but that is not very realistic. For once I will follow the flow and aim to improve on Earth's state of affairs. The following list concerns my suggestions how to improve on off-the-shelf photosynthesis:

Alien photosynthetic to-do list
- Have your photosynthesis process use a larger portion of the light falling on it
- Increase its affinity for CO2 (abolish photorespiration!) and improve reaction speed
- Increase its saturation point so it can use intense light
- Lower the compensation point so it can work with less light.

This 'to-do list' assumes that there are numerous biochemical pathways that can take in CO2, H2O and light and produce carbohydrates. Such processes may be centred on completely different pigments, sensitive to other wavelengths.

The illustration above has nothing to do with photosynthesis itself, but illustrates that there are many pigments in vision that are sensitive to varying wavelengths and to varying ranges of wavelengths. The pigment of the nectar-varying bat is interesting in that it is sensitive to a very broad range of light with a broad peak in the green area. A pigment like that, used for photosynthesis, would result in plants using light best where there is most of it, without throwing the rest away. Such plants would probably be a boring dark purplish grey.

You may well ask whether all this biochemical tinkering will make plants look different. If they still look like Earth plants but grow faster the exercise loses much of its appeal, doesn't it? I think they would look different: if leaves can use all light falling on them, that will have consequences for any leaves underneath; simple blobs or needles might replace complex leaves; the ability to have fewer leaves might induce trees to grow higher; plants might continue to grow through winter, etc., etc.

Of course, apart from biochemistry different biomechanical design principles will also result in differently looking plants. To see whether that approach yields interesting choices, we may need to travel back to the Silurian and Devonian and have a look at designs principles that came into being when land plants first struggled against gravity. Changing designs and changing plant biochemistry ought to result in enough 'alienosity' to please anyone. We'll see...